• Fisheries and Aquatic Sciences
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• v.2 no.2
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• pp.210-217
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• 1999

Chemical oxygen demand (COD), phytoplankton cell number and chlorophyll-a concentration (Chl-a), sediment mean grain size and ignition loss were studied to determine their temporal trends in the study area. Historical data of COD, cell number and Chl-a were gathered from the late 1960s or early 1980s to 1997, and trends in temporal domain were obtained from a simple regression. Sediments for grain size and ignition loss (as organic contents in sediments) were sampled from the Chokchon macrotidal flat bimonthly from September 1990 to November 1996, and were analyzed using the decomposition method of time series analysis. In general, the first three data showed increasing trends based on regression analysis. The trends of sediment grain size fluctuated in a neutral pathway while those of ignition loss yielded no increasing pattern. In contrast with the suggestions from Ahn and Choi (1998) who reported a coarsening variation in sediment grain size to be a cause of the directional and remarkable changes of macrofaunal communities in this area, we could not find such a corresponding variation pattern from our samples. In diagnosing eutrophication, a paradoxical phenomenon was encountered between the trends in water column (COD, cell number and Chl-a) and sediment (ignition loss) data. In this paper, we inferred the possible processes that produce the discrepancy. Some explanations and biological responses to eutrophication were predicted and discussed.

• Steel and Composite Structures
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• v.17 no.1
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• pp.21-46
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• 2014

This paper presents a simple n-order four variable refined theory for the bending and vibration analyses of functionally graded plates. By dividing the transverse displacement into bending and shear parts, the number of unknowns and governing equations of the present theory is reduced, and hence, makes it simple to use. The present theory is variationally consistent, uses the n-order polynomial term to represent the displacement field, does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. The governing equations are derived by employing the Hamilton's principle and the physical neutral surface concept. The accuracy of the present solutions is verified by comparing the obtained results with available published ones.

• Journal of Power Electronics
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• v.17 no.1
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• pp.212-221
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• 2017

Permanent-Magnet Synchronous Generators (PMSGs) are used widely in Wind Power Generation Systems (WPGSs), and the Vienna rectifier was recently proposed to be used as the generator-side converter to rectify the AC output voltage in PMSG-based WPGS. Compared to conventional six-switch two-level PWM (2L-PWM) converters, the Vienna rectifier has several advantages, such as higher efficiency, improved total harmonic distortion, etc. The motivation behind this paper is to verify the performance of direct-driven PMSG wind turbine system based-Vienna rectifier by using a simulated direct-driven PMSG WPGS. In addition, for the purpose of reducing the reactive power loss of PMSGs, this paper proposes an induced voltage sensing scheme which can make the stator current maintain accurate synchronization with the induced voltage. Meanwhile, considering the Neutral-Point Voltage (NPV) variation in the DC-side of the Vienna rectifier, a NPV balancing control strategy is added to the control system. In addition, both the effectiveness of the proposed method and the performance of the direct-driven PMSG based-Vienna rectifier are verified by simulation and experimental results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.3
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• pp.206-217
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• 1994

In this study, indoor thermal parameters were measured to investigate the characteristics of thermal environments and 212 occupants were questioned to evaluate Korean thermal comfort in office building in summer. Thermal and comfort sensations were estimated using PMV(Predicted Mean Vote) and ET* (New Effective Temperature) which are most widely used nowadays. Comparing this experimental result with international standards and that of other research, Korean thermal responses were discussed. It was found that TSV(Thermal Sensation Vote) is more sensitive than PMV to the variation of temperature and that the measured percentage of dissatisfied is higher than PPD(Predicted Percentage of Dissatisfied) in real office building environments. By regression analysis, the following regression equation has been obtained: TSV=0.461ET*-11.808 and neutral temperature is $25.6^{\circ}C$ in this case. Thermal comfort range based on 80% satisfaction is also $24.0{\sim}26.8^{\circ}C$, which is about $1^{\circ}C$ higher than that of ANSI/ASHRAE Standard.

• Korean Journal of Plant Taxonomy
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• v.49 no.4
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• pp.275-281
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• 2019

One key step in the plant restoration process is the collection of seeds from the field. For the selection of source populations of target plant species for translocation purposes (reintroduction or reinforcements), several approaches are possible. A practical method involves the use of data from reciprocal transplant studies. If no direct data are available, knowledge of population genetics and the phylogeography of the target species can serve as an alternative. In this short review, we briefly propose guidelines for those collecting seeds for plant species restoration based on population genetics theory, focusing on two main questions: Where does the plant material come from and how are sources designated, and how are seeds efficiently collected from local populations? While genetic data on a larger scale (phylogeography and population genetics) are needed to form a reply to the first question, similar data on a smaller scale (fine-scale genetic structures within populations) are necessary to shed light on the second issue.

• Journal of Astronomy and Space Sciences
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• v.27 no.4
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• pp.329-335
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• 2010

We investigate the sources of the variation of the high-latitude thermospheric neutral mass density depending on the interplanetary magnetic field (IMF) conditions. For this purpose, we have carried out the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEGCM) simulations for various IMF conditions under summer condition in the southern hemisphere. The NCAR-TIEGCM is combined with a new empirical model that provides a forcing to the thermosphere in high latitudes. The difference of the high-latitude thermospheric neutral mass density (subtraction of the values for zero IMF condition from the values for non-zero IMF conditions) shows a dependence on the IMF condition: For negative $B_y$ condition, there are significantly enhanced difference densities in the dusk sector and around midnight. Under the positive-$B_y$ condition, there is a decrease in the early morning hours including the dawn side poleward of $-70^{\circ}$. For negative $B_z$, the difference of the thermospheric densities shows a strong enhancement in the cusp region and around midnight, but decreases in the dawn sector. In the dusk sector, those values are relatively larger than those in the dawn sector. The density difference under positive-$B_z$ condition shows decreases generally. The density difference is more significant under negative-$B_z$ condition than under positive-$B_z$ condition. The dependence of the density difference on the IMF conditions in high latitudes, especially, in the dawn and dusk sectors can be explained by the effect of thermospheric winds that are associated with the ionospheric convection and vary following the direction of the IMF. In auroral and cusp regions, heating of thermosphere by ionospheric currents and/or auroral particle precipitation can be also the source of the dependence of the density difference on the IMF conditions.

• Korean Journal of Bronchoesophagology
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• v.5 no.2
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• pp.164-173
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• 1999

Background : cis-Diamminedichloroplatinum(Ⅱ)(cis-platin) has been exhibited similar to bifunctional alkylating agents in the cell and known as an effective anticancer drug. Although this agent is very beneficial to the cancer patients, it may also damage to the normal cell. Many side effects were developed. Objectives : This experiments was undertaken to pursue the effect of cis-Platin on the mucous variation of the trachea. Materials and Methods : The male of Sprague-Dawley strain were used as and experimental animals. The experimental animals were killed at 1, 3 days and 1, 2 and 3 weeks after the third injection of cis-Platin was administered 1.5mg/kg to intraperitoneal injection at once a week for three weeks. The trachea was fixed to neutral formaline and stained with alcian blue(pH 1.0)-PAS, alcian blue(pH 2.5)-PAS double stains and these preparation observed with light microscope. Results : 1. In the trachea stained with alcian blue(pH 2.5)-PAS double stain, the epithelial cells were constricted in the 1 week, In the 1st day, 3rd day and 1st week, acidic mucopolysaccharide was increased but in the 2nd week, neutral mucopolysaccharide was increase. 2. In the trachea stained with alcian blue(pH 1.0)-PAS double stain, the 1st and 3rd day exhibited sulfa mucopolysaccharide with moderately or weakly positive reaction. In the 1st week the sulfa mucopolysaccharide with strongly positive reaction was increased. In the 2nd and 3rd week, the sulfa mucopolysaccharide with weakly positive and non-sulfa or neutral mucopolsaccharide with negative reaction were modified. Conclusion : It is consequently suggested that cis-Platin induces reversible toxic damage to tracheal cells including goblet cell.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.241.1-241.1
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• 2014

The large-area high-power radio-frequency (RF) driven ion sources based on the negative hydrogen (deuterium) ion beam extraction are the major components of neutral beam injection (NBI) systems in future large-scale fusion devices such as an ITER and DEMO. Positive hydrogen (deuterium) RF ion sources were the major components of the second NBI system on ASDEX-U tokamak. A test large-area high-power RF ion source (LAHP-RaFIS) has been developed for steady-state operation at the Korea Atomic Energy Research Institute (KAERI) to extract the positive ions, which can be used for the NBI heating and current drive systems in the present fusion devices, and to extract the negative ions for negative ion-based plasma heating and for future fusion devices such as a Fusion Neutron Source and Korea-DEMO. The test RF ion source consists of a driver region, including a helical antenna and a discharge chamber, and an expansion region. RF power can be transferred at up to 10 kW with a fixed frequency of 2 MHz through an optimized RF matching system. An actively water-cooled Faraday shield is located inside the driver region of the ion source for the stable and steady-state operations of RF discharge. The characteristics and uniformities of the plasma parameter in the RF ion source were measured at the lowest area of the expansion bucket using two RF-compensated electrostatic probes along the direction of the short- and long-dimensions of the expansion region. The plasma parameters in the expansion region were characterized by the variation of loaded RF power (voltage) and filling gas pressure.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.2
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• pp.115-122
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• 2007

In this paper, a novel fault detection method for fault tolerant control is proposed when the NPC inverter has a open failure in the switching device. The open fault of switching device is detected by checking the variation of a leg-voltage in the neutral-point-clamped inverter and the two phases control method is used for continuously balance the three phases voltage to the load. It can be achieve the fault tolerant control for improving the reliability of the NPC inverter by the fault detection and reconfiguration. This method has fast detection ability and a simple realization for fault detection, compared with a conventional method. Also, this fast detection ability improved the harmful effects such as DC-link voltage unbalance and overstress to other switching devices from a delay of fault detection. The proposed method has been verified by simulation and experiment.

• Journal of Animal Science and Technology
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• v.61 no.2
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• pp.69-76
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• 2019

Maize which has very high omega-6 fatty acid content has been used as a main feed grain for Hanwoo beef production to increase marbling, and thus omega-6 to omega-3 fatty acids ratio in Hanwoo beef is expected to be biased. To elucidate the current status of omega fatty acids ratio in Hanwoo beef, fatty acid profiles of neutral lipid and phospholipid fraction were analyzed separately using 55 Hanwoo steers' longissimus dorsi muscle slaughtered at Pyeongchang, Korea from Oct. to Nov. 2015. In addition, an association study was conducted to evaluate associations between single nucleotide polymorphism (SNP) markers from references and omega fatty acid profiles in phospholipid of Hanwoo beef samples using analysis of variance (ANOVA). In neutral lipid fraction, composition of saturated and monounsaturated fatty acids was higher and polyunsaturated fatty acids was lower compared to those in phospholipid fraction. The mean n-6/n-3 ratios of Hanwoo were $56.059{\pm}16.180$ and $26.811{\pm}6.668$ in phospholipid and neutral lipid, respectively. There were three SNPs showing statistically significant associations with omega fatty acid content. GA type of rs41919985 in fatty acid synthase (FASN) was significantly associated with the highest amount of C20:5 n-3 (p = 0.031). CC type of rs41729173 in fatty acid-binding protein 4 (FABP4) was significantly associated with the lowest amount of C22:2n-6 (p = 0.047). AG type of rs42187261 in FADS1 was significantly linked to the lowest concentration of C20:4 n-6 (p = 0.044). The total n-6/n-3 ratio of the steer which has all four SNP types in above loci (27.905) was much lower than the mean value of the total n-6/n-3 ratio in phospholipid of the 55 Hanwoo steers ($56.059{\pm}16.180$). It was found that phospholipid and neutral lipid of Hanwoo have very high n-6/n-3 ratios compared to the reported data from different cow breeds. Four SNPs in genes related with fatty acid metabolism showed significant associations with the fatty acid profile of phospholipid and may have potential as SNP markers to select Hanwoo steers in terms of n-6/n-3 balance in the future.